You would need a lot of CON or lone wolf to really benefit of a high AP per turn with Raistlin. No use having 20ap per turn when you can only get, say, 14 max. That would be 6AP wasted because you can't even use them, and you're still standing with a diminished health pool.
And as you mentioned, you would still want some initiative anyway.
Just dish one or two points in speed and you're good to go. With Way of the Warrior rank 5, which can be obtained quite quickly especially when you don't really have anything more useful to boost, you will gain +4 AP per turn anyway.
